137 research outputs found
Cabibbo suppressed decays and the lifetime
The problem of the lifetime is considered in the framework of
{\em Heavy-Quark Expansion} and symmetry. The lifetime of
is expressed in terms of measurable inclusive quantities of the
other two charmed baryons belonging to the same multiplet in a
model-independent way. In such a treatment, inclusive decay rates of singly
Cabibbo suppressed decay modes have a prominent role. An analogous approach is
applied to the multiplet of charmed mesons yielding interesting predictions on
properties. The results obtained indicate that a more precise
measurement of inclusive decay quantities of some charmed hadrons (such as
) that are more amenable to experiment can contribute
significantly to our understanding of decay properties of other charmed hadrons
(such as ) where discrepancies or ambiguities exist.Comment: 9 pages, revtex4; certain improvements in text as suggested by the
referee, acknowledgement changed; version to appear in Phys. Rev.
Perturbative QCD Fragmentation Functions for Production of P-wave Mesons with Charm and Beauty
We calculate the leading order QCD fragmentation functions for the production
of -wave charmed beauty mesons. Long-distance effects are factored into two
nonperturbative parameters: the derivative of the radial wavefunction at the
origin and a second parameter related to the probability for a
heavy quark pair that is produced in a color-octet -wave state to form a
color-singlet -wave bound state. The four states and those states
which lie below the flavor threshold eventually all decay into the
ground state through hadronic cascades or by emitting photons. The total
fragmentation probabilities for production of the ground state from
the cascades of the and states are about and
respectively. Thus the direct production of the -wave
states via fragmentation may account for a significant fraction of the
inclusive production rate of the at large transverse momentum in high
energy colliders. Our analytic results for the -wave fragmentation functions
disagree with those obtained earlier in the literature.Comment: 31 pages, Latex file, 1 figure (postscript file appended at the end
Lifetimes of Heavy-Flavour Hadrons -- Whence and Whither?
A theoretical treatment for the weak decays of heavy-flavour hadrons has been
developed that is genuinely based on QCD. Its methodology as it applies to
total lifetimes and the underlying theoretical issues are sketched. Predictions
are compared with present data. One discrepancy emerges: the beauty baryon
lifetime appears to be significantly shorter than expected. The ramifications
of those findings are analyzed in detail.Comment: 15 pages, no figures, LATEX, two references added and new information
concerning a lower charm content in B decays incorporate
A Tracker Solution for a Holographic Dark Energy Model
We investigate a kind of holographic dark energy model with the future event
horizon the IR cutoff and the equation of state -1. In this model, the
constraint on the equation of state automatically specifies an interaction
between matter and dark energy. With this interaction included, an accelerating
expansion is obtained as well as the transition from deceleration to
acceleration. It is found that there exists a stable tracker solution for the
numerical parameter , and smaller than one will not lead to a physical
solution. This model provides another possible phenomenological framework to
alleviate the cosmological coincidence problem in the context of holographic
dark energy. Some properties of the evolution which are relevant to
cosmological parameters are also discussed.Comment: 10 pages, 3 figures; accepted for publication in Int.J.Mod.Phys.
Renormalization-group running cosmologies - a scale-setting procedure
For cosmologies including scale dependence of both the cosmological and the
gravitational constant, an additional consistency condition dictated by the
Bianchi identities emerges, even if the energy-momentum tensor of ordinary
matter stays individually conserved. For renormalization-group (RG) approaches
it is shown that such a consistency relation ineluctably fixes the RG scale
(which may have an explicit as well as an implicit time dependence), provided
that the solutions of the RG equation for both quantities are known. Hence,
contrary to the procedures employed in the recent literature, we argue that
there is no more freedom in identification of the RG scale in terms of the
cosmic time in such cosmologies. We carefully set the RG scale for the RG
evolution phrased in a quantum gravity framework based on the hypothetical
existence of an infrared (IR) fixed point, for the perturbative regime within
the same framework, as well as for an evolution within quantum field theory
(QFT) in a curved background. In the latter case, the implications of the scale
setting for the particle spectrum are also briefly discussed.Comment: v1:15 pages, 1 figure. v2: references added. v3: discussion of the
physical interpretation of the scale-setting procedure added. v4: discussions
added. Version to appear in Phys. Rev.
OSOBA SA PSIHIČKIM POREMEĆAJEM POČINITELJ PROTUPRAVNIH DJELA U ZATVORSKOM SUSTAVU - PRIKAZ SLUČAJA I PREGLED ZAKONSKIH PROPISA KOJI REGULIRAJU POSTUPANJE
Prikazan je slučaj bolesnika hospitaliziranog na Odjelu forenzičke psihijatrije Zatvorske bolnice u Zagrebu pod dijagnozama
Trajna promjena ličnosti nakon katastrofičnog događaja (proizašla iz kroničnog PTSP) i Ovisnost o alkoholu,
koji je uz kaznu zatvora imao izrečenu sigurnosnu mjeru obveznog psihijatrijskog liječenja po čl. 68. novog Kaznenog
zakona (član 75. starog KZ-a). U sklopu pojedinačnog programa izvršavanja kazne zatvora bolesnik je uključen u
bio-psiho-socijalni model liječenja i rehabilitacije. U radu je prikazan i osvrt na zakonom propisane postupke prema
osobama sa psihičkim poremećajem koje su počinile neko protupravno djelo. Ako je osoba počinila lakše protupravno
djelo procesuira se po Prekršajnom zakonu, Zakonu o zaštiti od nasilja u obitelji i Zakonu o zaštiti osoba sa psihičkim
poremećajem, koje sankcije se provode na slobodi u forenzičnim ambulantama javnog zdravstva ili psihijatrijskim odjelima
bolnica javnog zdravstva. U slučajevima kada je osoba počinila teže kazneno djelo sudski se postupci provode u
skladu s odredbama Zakona o kaznenom postupku, Kaznenog zakona i Zakona o zaštiti osoba s psihičkim poremećajem,
a tretman se provodi unutar zatvorskog sustava, ako je osoba bitno smanjeno ubrojiva i uz kaznu zatvora joj je izrečena
sigurnosna mjera obveznog psihijatrijskog liječenja (čl.68. KZ/11) ili liječenja od ovisnosti (čl. 69. KZ/11), odnosno na
forenzičkim odjelima javnog zdravstva, ako se radi o neubrojivoj osobi koja je zbog svog psihičkog poremećaja opasna
za okolinu
Four-quark Operators Relevant to B Meson Lifetimes from QCD Sum Rules
At the order of 1/m_b^3, the B meson lifetimes are controlled by the hadronic
matrix elements of some four-quark operators. The nonfactorizable magnitudes of
these four-quark operator matrix elements are analyzed by QCD sum rules in the
framework of heavy quark effective theory. The vacuum saturation for
color-singlet four-quark operators is justified at hadronic scale, and the
nonfactorizable effect is at a few percent level. However for color-octet
four-quark operators, the vacuum saturation is violated sizably that the
nonfactorizable effect cannot be neglected for the B meson lifetimes. The
implication to the extraction of some of the parameters from B decays is
discussed. The B meson lifetime ratio is predicted as
\tau(B^-)/\tau(B^0)=1.09\pm 0.02. However, the experimental result of the
lifetime ratio \tau(\Lambda_b)/\tau(B^0) still cannot be explained.Comment: 20 pages, latex, 6 figures, discussion on non-factorizable effect of
the four-quark condensate added, to appear in Phys. Rev. D57 (1998
Hadronic Production of Doubly Charmed Baryons via Charm Exitation in Proton
The production of baryons containing two charmed quarks Xi_cc in hadronic
interactions at high energies and large transverse momenta is considered. It is
supposed, that Xi_cc-baryon is formed during a non-perturbative fragmentation
of the (cc)-diquark, which was produced in the hard process of -quark
scattering from the colliding protons: c+c -> (cc) +g. It is shown that such
mechanism enhances the expected doubly charmed baryon production cross section
on Tevatron and LHC colliders approximately 2 times in contrast to predictions,
obtained in the model of gluon - gluon production of (cc)-diquarks in the
leading order of perturbative QCD.Comment: LaTeX2e, 13 pages plus 4 fig. using revtex4.sty, epsfig.sty. Talk was
presented at International Seminar on Physics of Fundamental Interactions in
ITEP, Moscow, Russia, November 27 - December 1, 200
P-Wave Charmonium Production in B-Meson Decays
We calculate the decay rates of mesons into P-wave charmonium states
using new factorization formulas that are valid to leading order in the
relative velocity of the charmed quark and antiquark and to all orders in the
running coupling constant of QCD. We express the production rates for all four
P states in terms of two nonperturbative parameters, the derivative of the
wavefunction at the origin and another parameter related to the probability for
a charmed-quark-antiquark pair in a color-octet S-wave state to radiate a soft
gluon and form a P-wave bound state. Using existing data on meson decays
into to estimate the color-octet parameter, we find that the
color-octet mechanism may account for a significant fraction of the
production rate and that mesons should decay into at a similar
rate.Comment: 14 page
Holographic Dark Energy Like in Gravity
We investigate the corresponding relation between gravity and
holographic dark energy. We introduce a kind of energy density from
which has role of the same as holographic dark energy.
We obtain the differential equation that specify the evolution of the
introduced energy density parameter based on varying gravitational constant. We
find out a relation for the equation of state parameter to low redshifts which
containing varying correction.Comment: 10 page
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